JPS62154230A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the wear resistance of a magnetic layer while suppressing the wear of a magnetic head by incorporating inorg. carbide powder and inorg. oxide powder of the same element common with the inorg. carbide in combination into the magnetic layer. CONSTITUTION:The inorg. carbide powder having >=1,500kg/mm<2> Vickers hardness and the inorg. oxide powder of the same element common with the inorg. carbide are incorporated into the magnetic layer. The same element common with the inorg. carbide powder and the inorg. oxide powder is specified to any element selected from Si, Ti, Zr, W, Ta, V, Nb, Hf, and B. The intended effect is not obtainable with the inorg. carbide powder of any selected element if the average particle size thereof is 0.1mum or smaller. There is the possibility of wear of a magnetic head if the powder having >=0.7mum size is used. The intended effect is not obtainable with the inorg. oxide powder if the average particle size thereof is <=0.02mum. The surface roughness of the magnetic layer is poor and the electromagnetic conversion characteristic is low if the powder having >=1.0mum size is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium with excellent durability.

[Conventional technology]

In general, magnetic recording media, which are made by coating a magnetic paint consisting of magnetic powder, binder resin, organic solvent, and other necessary components on a substrate such as a polyester film, are subject to intense rubbing against magnetic heads during recording and playback. Since the magnetic layer is in contact with the magnetic layer, it is easily abraded, and a magnetic layer that is less abraded and has excellent durability is required.

In particular, in recent years, the demand for high-density recording in magnetic recording media has become higher and higher. However, while the recording density improves as finer magnetic powder is used, the mechanical strength of the magnetic layer becomes weaker, and metallic iron magnetic powder, alloy magnetic powder, etc. Since iron oxide magnetic powder is relatively soft compared to iron oxide magnetic powder, the recording density is similarly improved, but the mechanical strength of the magnetic layer is weakened, and the magnetic layer is easily worn out.

Therefore, as a measure to improve the wear resistance of the magnetic layer, for example, an inorganic powder with a Mohs hardness of 6 or more, such as Cr2O3 powder or No\1203 powder, is mixed into the magnetic layer. However, when such inorganic powders with a Mohs hardness of 6 or more are used, the wear resistance of the magnetic recording medium is considerably improved, but the wear of the magnetic head that makes sliding contact with the magnetic layer is increased. This has the disadvantage that it shortens the life of the magnetic head.

Therefore, in order to improve such drawbacks, in addition to these inorganic powders with a Mohs hardness of 6 or more, TiO2 powder, SiO2 powder, and ZrO2 powder, which have a slightly smaller hardness than these, are used.
Attempts have been made to suppress the wear of the magnetic head by adding flavoring powders capable of suppressing the wear of the magnetic head, such as powder and CX-Fe203 powder, and using these together.

(JP-A-56-13525, JP-A-57-12421
No., JP-A-57-24026, JP-A-57-5553
(No. 3, JP-A-57-183628) [Problems to be solved by the invention] However, these inorganic powders with a Mohs hardness of 6 or more,
Simply using inorganic powders that can suppress the wear of magnetic heads in combination cannot sufficiently improve the wear resistance of the magnetic layer and sufficiently suppress the wear of the magnetic heads. No material has been obtained that sufficiently improves wear resistance while sufficiently suppressing the wear of the throat.

[Means for solving problems]

This invention was made as a result of various studies in view of the above circumstances, and uses an inorganic carbide powder with a Vickers hardness of 1500 kg/m or more and an R-free oxide powder of the same element as the inorganic carbide. By incorporating it into the magnetic layer, the wear resistance of the magnetic layer is sufficiently improved while the wear of the magnetic head is sufficiently suppressed.

The carbide powder used in this invention is preferably an inorganic carbide powder with a Bierker's hardness of 1500 kg/mr or more, and a Vickers hardness of 1,500 kg/mr.
When it is +f or more, the inorganic carbide powder is relatively hard and the wear resistance of the magnetic layer is sufficiently improved. In addition, the inorganic oxide powder that has the same element in common with this inorganic carbide powder is relatively softer than the inorganic carbide powder that has the same element in common, so this type of inorganic oxide powder sufficiently suppresses the wear of the magnetic head. be done. Furthermore, since both have the same element in common, they have good affinity in the magnetic layer and are uniformly dispersed in the magnetic layer. Therefore, when these two are used together, the effect of reinforcing the magnetic layer can be fully exhibited without causing wear on the magnetic head, and the wear resistance of the magnetic layer can be sufficiently improved while sufficiently suppressing wear on the magnetic head. Ru.

Examples of such inorganic carbide powders having a carth hardness of 1500 kg/mm or more include Si, Ti, Zr, W, and Ta.
, V, Nb, , Hf, and B are preferably used, and as the oxide inorganic powder, inorganic oxide powders of these elements are preferably used. Such S i, ′r i,
The inorganic carbide powder of any element selected from Zr, W, Ta, ■, NbXHf, and B has an average particle size of 0.
If the particle size is smaller than 1 μm, the desired effect cannot be obtained, while if the particle size is larger than 0.7 μm, the magnetic field may be damaged by 1 μm.
It is preferable to use one within the range of ~0.7 μm,
Furthermore, if the average particle size of the inorganic oxide powder is smaller than 0.02 μm, the desired effect will not be obtained, and if the average particle size is larger than 1.0 μm, the surface roughness of the magnetic layer will deteriorate.
Because the electromagnetic conversion characteristics deteriorate, the average particle diameter is 0.02~
It is preferable to use one within the range of 1.0 μm.

The mixing ratio of such an inorganic carbide powder with a Vickers hardness of 1500 kg/mm or more and an inorganic oxide powder of the same common element is 1:9 to 9 in terms of weight ratio (inorganic carbide powder to inorganic oxide powder). It is preferable that the amount is within the range of 1. If the amount of inorganic carbide powder is too small, the wear resistance of the magnetic layer will not be sufficiently improved, and if the amount of inorganic oxide powder is too small, the wear of the magnetic head will not be sufficiently suppressed. . In addition, the amount of the inorganic carbide powder having the same common element and the R-free oxide powder combined in such a blending ratio is 0.5 to 15% by weight based on the magnetic powder. It is preferable to keep it within the range; if it is too small, the desired effect will not be obtained.
If the amount is too large, the amount of magnetic powder will be relatively reduced, which may lead to deterioration of electromagnetic conversion characteristics, which is not preferable.

In this way, when an inorganic carbide powder with a Vickers hardness of 1500 kg/mm or more and an inorganic oxide powder are used in the above-mentioned proportions, an excellent magnetic layer of the inorganic carbide powder can be obtained. The reinforcing function and the excellent magnetic head wear suppression effect of the inorganic oxide powder are fully demonstrated, and the electromagnetic conversion characteristics do not deteriorate, the magnetic layer is not scratched, or the busy magnetic head is not worn out. The wear resistance of the magnetic layer is sufficiently improved. Such an effect can be sufficiently produced no matter what kind of magnetic powder is used! However, especially when using fine particles with a particle size of 0.3 μm or less, or magnetic powders that cannot reinforce the mechanical strength of the magnetic layer, such as gold mud magnetic powder or composite magnetic powder, the effect becomes even more effective. is demonstrated.

Examples of magnetic powder include r-Fe203 powder, F
In addition to e3O4 powder, Co-containing r-Fe20° powder, Co-containing Fe3O4 powder, and CrO2 powder, various conventionally known magnetic powders such as Fe powder, Co powder, Fe-'Ji powder, and barium ferrite powder bed are widely used. .

In addition, binder components of the 1IfI magnetic powder include vinyl chloride-vinyl acetate copolymers, cellulose resins, polyurethane resins, polyester resins, acrylic resins, rubber resins, isocyanate compounds, etc. It is widely used as

The magnetic recording medium of the present invention may be manufactured according to a conventional method. For example, the above-mentioned inorganic carbide powder having the same common element and inorganic oxide powder may be mixed into magnetic powder, binder resin, organic A magnetic paint is prepared by mixing and dispersing it with a solvent, etc., and it is applied onto a substrate such as a polyester film.
It may be applied by any coating means such as a coater and dried.

In addition, various additives commonly used in magnetic paints,
For example, fatty acids, fatty acid esters, silicone 1I
Lubricants and dispersants such as 11 lubricants, fluoride, base type/I2I additives, antistatic agents such as carbon blank, etc. may be optionally added and used.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 cr-F13 powder (particle size 0.2pm loO\ti
m part, specific surface area by BET method: ;5 m/g) SiC powder (particle size 0.3 μm 6 //Vickers hardness approximately 3000 kg/mm) Si02
Powder (particle size 01lI!m1 or less) n-butyl stearate 2 V A G
11 (manufactured by U, C, C Company, vinyl chloride 14''-vinyl acetate-vinyl alcohol copolymer) Vandenox T-5201 (k, 10 = manufactured by Nippon Ink Chemical Co., Ltd., polyurekne resin) Cyclohexanone 901-methyl Isobutyl ketone 90″ toluene
90 After dispersing this composition in a ball mill for 100 hours, 4 m of Desmodulite (manufactured by Bayer AG, trifunctional low molecular weight isocyanate compound) was added to the bottom, and the mixture was further uniformly mixed and dispersed for 1 hour to prepare a magnetic paint. did. This magnetic paint was applied onto a polyester film with a thickness of 10 μm so that the dry J'g was 3 μm, dried, calendered, and then cut into 1/2 inch width to make a videotape. .

Example 2 In the first formation of the magnetic paint in Example 1, the same amount of TiC powder (particle size 0.3 μm, Vickers hardness approximately 2000 kg/mm) was used instead of SiC powder, and Si
Instead of O2, TiO2 powder (particle size 0.2 μm
A videotape was produced in the same manner as in Example 1, except that 3E1 parts of (3E1) were used.

Example 3 In the composition of the magnetic paint in Example 2, α-Fe powder was replaced with Co %) J-attached r-Fe20,1°5) (particle size 0.3 μm, specific surface area 45rr by BET method).
A videotape was made in the same manner as in Example 1, except that the same amount of cyclohexanone, methyl isobutyl ketone, and toluene were used, and the amounts of cyclohexanone, methyl isobutyl ketone, and toluene were changed from 90 parts by weight to 9 parts by weight, respectively.

Comparative Example 1 Same as Example 1 except that the same amount of α-A1203 powder (particle size 0.3 μm, Vickers hardness about 2000 kg/mn?) was used instead of SiC powder in the composition of the magnetic paint in Example 1. I made a videotape in the same way.

Comparative Example 2 Video was produced in the same manner as in Example 1, except that in the composition of the magnetic paint in Example 2, the same amount of SiC powder (particle size 0.3 μm, Vickers hardness approximately 3000 kg/mm) was used instead of TiC powder. I made a tape.

Comparative Example 3 Same as Example 1 except that the same amount of α-A1203 powder (particle size 0.3 μm, Vickers hardness about 2000 kg/mm) was used instead of SiC powder in the composition of the magnetic paint in Example 3. I made a videotape.

The video tapes obtained in each of the Examples and Comparative Examples were mounted on a commercially available VTR, and the wear amount and still life of the magnetic head were measured using the following methods.

<Amount of Wear of Magnetic Head> Amount of wear of the magnetic head after running a video tape for 100 hours was measured by a change in the amount of protrusion of the head from the cylinder.

<Still Life> A videotape was played back in still mode, and the time required for the playback output level to drop by 20 dB from the initial value was measured.

Table 1 below shows the results.

Table 1 As is clear from Table 1 above, the videotapes obtained in Examples 1 to 3 had longer still lifes and magnetic fields compared to those obtained in Comparative Examples 1 to 3. The amount of wear on the head is small, which indicates that the magnetic recording medium obtained by the present invention can sufficiently suppress wear on the magnetic head and has sufficiently improved durability.

Claims (1)

[Claims] 1. The magnetic layer has a Vickers hardness of 1500 kg/mm.
Magnetic recording medium 2 characterized in that it contains at least ^2 inorganic carbide powder and an inorganic oxide powder having the same element in common with the inorganic carbide, the inorganic carbide powder and the inorganic oxide powder having the same element in common. is Si, Ti, Zr, W, Ta, V, Nb,, Hf
, B. The magnetic recording medium according to claim 1, which is selected from